The obligate reliance of freshwater mussels on aquatic vertebrates
as hosts of glochidia creates significant complications in understanding mussel
life history and demography, and in development of effective conservation
strategies.The typical approach for
identifying these hosts is via laboratory trials that identify potential host
species, but do not reveal which of these species are actually used by mussel
populations.Laboratory trials
identified 23 of 30 species as potential hosts for Popenaias popeii.We
conducted repeated surveys of fishes from the Black River, NM to determine
which species were infested with P.
popeii glochidia, and to measure the prevalence and intensity of
infestations.We calculated an
“ecological host index” that integrates fish abundance with infestation
prevalence and intensity.Surveys
collected 2,115 individuals from 14 species of fish; of these, 249 individuals
of 14 species had encysted glochidia.Three
species of catostomids had relatively low-to-moderate abundance, moderate-to-high
prevalence, and high intensity of infestations; one species of cyprinid had
moderate abundance, high prevalence and high intensity.All other species had low abundance or
prevalence, and low intensity.Carpiodes carpio, Moxostoma congestum,
and Cyprinella lutrensis had much
higher ecological host indices than any other species.Infestations on benthic-dwelling catostomids
were on the face and operculum, while those on the water-column-dwelling C. lutrensis were on the gills.We conclude that the list of ecologically
relevant host species is much smaller than the list of potential hosts
identified in laboratory trials.Successful conservation and restoration of unionid populations will
require the presence of this much smaller set of host species.